In many optical devices, including light sources such as LEDs and semiconductor lasers and light collectors such as solar voltaic cells, it is in general desirable to limit the operating temperature in order to keep the conversion efficiency at high levels. For this purpose, it is often desirable to extract heat from an optoelectronic device (LED, laser, or solar cell). For this purpose a metallic heat spreader with radiator fins can be attached to the optoelectronic device, but will block light. Consequently, the light going to or from the device should not intercept the heat sink, else it will be wasted heating the heat sink. This condition precludes the use of some optical designs, such as the XR (defined in U.S. Pat. No. 6,639,733, which is incorporated herein by reference in its entirety). In general, an XR configuration has a reflective surface (X) followed by a refractive surface (R), and the optoelectronic device is typically placed approximately in the aperture of these optical designs (which is where the light enters or exits the optical system). Thus an opaque heat sink would block the light flow. Although the optoelectronic device is typically small compared to the aperture, and so blocks little of the light flow, an attached heat sink large enough to be useful is typically not so small. The reason for the optoelectronic device being smaller than the optical system aperture is the very function of the optical system, transforming nearly hemispheric light going to or from the optoelectronic device into a more nearly collimated beam that is necessarily much larger, because of etendue conservation. That is, for this transformation to be efficiently done requires that the cross-section area of the collimated beam (i.e., the area of the aperture) be larger than the area of the hemispheric light, which is in fact the emitting or receiving area of the optoelectronic device.
Optical designs that are precluded by an opaque heat sink (such as the XR) have a mirror whose size is similar to that of the aperture. These optical designs are convenient for several reasons: a compact aspect ratio, high effectiveness over large wavelength ranges, and potentially low cost. The present system allows these optical designs to be used with heat extraction apparatus. This is important because the XR concentrator is a candidate for large-scale solar-power deployment, and several in particular are the subject of patent applications by the same inventors: U.S. patent application Ser. No. 12/206,547 filed Sep. 8, 2008 titled “Multi-Junction Solar Cells With a Homogenizer System and Coupled Non-imaging Concentrator”, U.S. patent application Ser. No. 11/997,142 filed Jun. 30, 2008 (publication No. U.S. 2008-316761 A1) titled “Free-Form Lenticular Optical Elements and their Application to Condensers and Headlamps and corresponding WO 2007/016363; and U.S. patent application Ser. No. 12/075,830 filed Mar. 14, 2008 (publication no. U.S. 2008-0223443 A1) titled “Optical Concentrators, Especially for Solar-Photovoltaics” and incorporated by reference in their entirety.